Professor John Marshall is the Frost Professor of Ophthalmology and Chairman of the Academic Department of Ophthalmology at St. Thomas’ Hospital and was formerly Sembal Professor of Experimental Ophthalmology at the Institute of Ophthalmology from 1982-1991. His research over the past 40 years has ranged over a number of ocular problems but has concentrated on the inter-relationships between light and aging, the mechanisms underlying age-related, diabetic, and inherited retinal disease, and the development of lasers for use in ophthalmic diagnosis and surgery. This work has resulted in almost 400 research papers, numerous book chapters and books, and has produced and patented the revolutionary excimer laser for the correction of refractive disorders, with more than 17 million procedures undertaken worldwide. His research has also created the world’s first diode laser for treating eye problems of diabetes, glaucoma, and aging. He is editor and co-editor of numerous international journals. He has been awarded the Nettleship Medal of the Ophthalmological Society of the United Kingdom, the Mackenzie Medal, the Raynor Medal, the Ridley Medal, the Ashton Medal, the Ida Mann Medal and the Lord Crook Gold Medal of the Worshipful Company of Spectacle Makers, the Doyne Medal of the Oxford Congress, the Barraquer Medal of the International Society of Cataract and Refractive Surgery, the Kelman Innovator Award of the American Society for Refractive and Cataract Surgery, and the Lim Medal of the Singapore National Eye Centre. He has been visiting professor at numerous universities on every continent. He has held posts chairing the medical advisory boards of many international companies and was a director of Diomed for some years, this being the leading supplier of diode laser systems for surgery.